Fuel injection apparatus for reciprocating internal combustion engines



' April 30, 1957 A. L. FUEL INJECTION APPAR Filed NOV. 29, 1954 CATFORD ATUS FOR RECIPROCATING -BY y/QZZ INTERNAL COMBUSTION ENGINES I 2 Sheets-Sheet l |NVENTOR ADEIAN L. CATFoRb W M MX- ATTORN EYS April 30, 1957 Filed Nov. 29, 1954 A. L. CATFORD FUEL INJECTION APPARATUS FOR RECIPROCATING INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 2 m 'Q l Qm Q Q a: m lk? "1 n/E Q@ Y O to W Q o- K9 b o Q a N 39 3 00 v x 3 OOOOO I o 0000c; Q a "0 N Q *0 n INVENTOE AbQlAN Lon-rmwflvlew BY WW ATTORNEYS United States Patent FUEL INJECTION APPARATUS FOR RECIP- ROCATING INTERNAL COMBUSTION EN- GINES Adrian Leslie Catford, Hampton, England, assignor to D. Napier & Son Limited, London, England, a com- P y Application November 29, 1954, Serial No. 471,869

Claims priority, application Great Britain December 1, 1953 8 Claims. (Cl. 123-140) This invention relates to fuel injection apparatus for reciprocating internal combustion engines of the liquid fuel injection type and of the kind in which the fuel is delivered to the one or more injection nozzles of the engine in metered quantities and at the appropriate moments by a reciprocating fuel injection pump.

In existing fuel injection apparatus of the above kind the quantity of fuel delivered during each delivery stroke of a pump plunger is varied in accordance with the desired operating conditions of the engine by control mechanism arranged to vary the effective length of the plunger delivery strokes, the most usual arrangement being one in which the pump plunger is formed and arranged to act as a valve which renders the earlier and later parts of the plunger delivery stroke inoperative and has a helical cut-off edge so that by rotating the plunger relatively to its cylinder the length of the effective intermediate part of the plunger delivery stroke can be varied. The present invention is not limited, however, to apparatus embodying injection pumps of this kind but is applicable to apparatus embodying any form of reciprocating fuel injection pump having control means by which the effective length of each plunger delivery stroke can be varied.

With fuel injection apparatus embodying pumps of the above general kind as at present used, it is found that the quantity of fuel delivered through the injection noz zles at any given pump setting tends to change with any changes made in the part of the fuel injection system between the pump and the engine cylinder or cylinders, such for example as changes in the length of the fuel lines between the pump and the injection nozzles or changes in the design, or opening pressure of the injection nozzles, and one object of the present invention is to provide fuel injection apparatus in which the quantity of fuel delivered during each plunger delivery stroke will tend to be more exactly determined irrespective of changes which may be made or may occur in the characteristics of the part of the injection apparatus on the engine side of the injection pump.

Fuel injection apparatus for a reciprocating internal combustion engine of the liquid fuel injection type according to the present invention comprises a reciprocating fuel injection pump arranged to receive fuelfrom a pump supply chamber, mechanism for varying the rate at which fuel is delivered by the pump to the engine, means for supplying fuel to the pump supply chamber at a controlled net rate of flow, including at least one metering orifice arranged so that the volumetric rate of fuel flow therethrough determines the net volumetric rate at which fuel is supplied to the injection pump supply chamber, and pressure responsive means arranged to be responsive to changes in the pressure developed across the orifice, and to act on the control mechanism for varying the quantity of fuel delivered by the pump to the engine, in a sense tending to maintain the pressure developed across the orifice at a constant value, and hence to' 2,790,433 Patented Apr. 30, 1957 maintain a constant controlled delivery of fuel from the pump to the engine.

For convenience herein reference is made to the net volumetric rate of flow to the injection pump supply chamber, which expression is to be understood as referring to the volumetric rate at which, but for the with drawal of fuel by the injection pump, the volume of fuel in the injection pump supply chamber would be increasing at any moment. Thus in a simple case where the injection pump supply chamber is closed except for the delivery passage or passages by which the injection pump is fed and employing a single inlet metering orifice, this rate would be the rate at which fuel passes through the inlet metering orifice into the injection pump supply chamber. In other cases, however, there may be a con tinuous flow of fuel both to and from the injection pump supply chamber respectively through inflow and outflow metering orifices, in Which case the volumetric rate referred to would be the rate at which the flow through the inflow orifice exceeds that through the outflow orifice.

In most cases in fact, apparatus according to the invention would employ a fuel injection pump of the kind in which part of each plunger delivery stroke is inoperative to deliver fuel to an injector and merely returns fuel to the supply chamber, and in this case, in' view of the tendency for air bubbles to form in the fuel returned to the chamber by the plungers, it may be desirable to provide for a continuous circulation of fuel through the chamber to carry such air bubbles away.

Thus according to a preferred feature of the invention the means for supplying fuel to the pump supply chamber include means for removing fuel continuously therefrom, and the apparatus includes metering orifices in both the inlet and outlet connections to the pump supply chamber, one of such orifices being associated with the said pressure responsive means, while the other orifice is associated with means for maintaining a controlled rate of flow therethrough.

In any case the apparatus preferably includes master control means arranged to adjust the effective crosssectional area of the orifice or one of the orifices, in relation to the pressure difierence developed across said orifice, so as to vary the net volumetric supply of fuel to the pump supply chamber.

Thus in one preferred construction the first metering orifice (the pressure drop across which is arranged to control the control mechanism for varying the fuel delivered to the engine by the pump) is arranged in the inlet connection to the injection pump supply chamber, and the master control means is arranged to adjust the cross sectional area of this orifice, while the second metering orifice is arranged in the outlet connection from the pump supply chamber, and is of fixed cross sectional area, and means are provided for varying the flow through the outlet connection in accordance with the pressure difference developed across this 'second orifice, so as to maintain a constant fuel fiow through the outlet connection from the pump supply chamber.

In another preferred construction the first metering orifice (the pressure drop across which is arranged to control the control mechanism for varying the fuel delivered to the engine by the pump) is of fixed cross sectional area and is arranged in the outlet connection from the pump supply chamber, while the second metering orifice is arranged in the inlet connection to the pump supply chamber, and the master control means is arranged to adjust the cross sectional area of this orifice.

Preferably the master control means is arrange-d to adjust also directly the setting of the control mechanism for varying the rate at which fuel is delivered by the pump to the engine.

And in this case the apparatus will preferably include a differential transmission'system between the master control means, the control mechanism of the pump, and an element responsive to the pressure drop developed across the metering orifice associated therewith.

In any case it will be understood that the apparatus may include means for automatically varying the effective cross sectional area of one of the orifices in accordance with the specific gravity of the fuel, so as to control the mass fuel flow delivered by the pump to the engine.

Moreover, although the control of the volumetric rate of flow through a metering orifice in apparatus according to the invention for the purpose of controlling the volumetric rate of flow of fuel into the injection pump supply chamber as above defined would usually be effected by varying the effective cross-sectional area of the orifice, it could in some cases be effected by varying the pressure drop across the orifice, for example by varying the pressure at which the pressure-responsive means is set to maintain the fuel in the injection pump supply chamber, or by varying both the cross-section of the orifice and the pressure drop across it.

The invention may be performed in various different ways but two specific embodiments will now be described by way of example with reference to the accompanying drawings in which:

Figure l is a somewhat diagrammatic view partly in section of a fuel injection system with a constant-flow return of fuel from the injection pumps, and

Figure 2 is a similar view of a fuel injection system with a constant delivery of fuel to the pumps and a variable fiow return.

Fuel injection pump assemblies are of known kind, comprising a plurality of plungers arranged to draw fuel from the chambers 1 and 2 and to return surplus fuel thereto during the idle parts of their delivery strokes. The quantity of fuel returned is varied by rotating the plungers about their axes, conveniently by means of a rack (not shown) engaging pinions on the plungers. The setting of the fuel injection pumps, that is to say the quantity of fuel to be delivered by each plunger during its delivery stroke, is controlled in known manner by a pair of arms 13, 14 connected respectively to the racks acting on the plungers.

In the example illustrated in Figure l the two banks of fuel injection pumps 1 and 2 are supplied with fuel from a gear type pump 3 and the system is of the constant flow return type, in which an excess of fuel is constantly delivered to the fuel supply chambers, and this excess is constantly being returned to the fuel reservoir. In the system illustrated in Figure 2 the pump 3 receives fuel from a fuel tank 40 via a filter 41 and delivers the fuel under pressure via a second filter 42 to a metering orifice assembly indicated generally at 43, and thence via a conduit 44 to the injection pump supply chambers 1 and 2. From the pump supply chambers 1 and 2 the excess fuel passes via a conduit 45 to a constant-flow control unit indicated generally at 46 and thence via a return conduit 47 to the tank 40.

The fuel pump 3 is mounted in a casing including a pressure relief valve 48 maintaining a substantially constant pressure at the output side of the pump and a relief valve 49 which by-passes fuel through the pump if the pressure on the low pressure side should for any reason rise above a predetermined value.

The constant flow unit 46 comprises a fixed orifice 50 through which the whole of the excess fuel in the conduit 45 passes, and a second orifice 51 of variable cross sectional area, arranged in series with the orifice 50, the effective area of the orifice 51 being controlled by a conical valve member 52 under the control of a servooperated piston 53. The servo piston 53 is controlled by a balanced shuttle valve 54 which is connected at one end to a diaphragm 55 subject on either side to the pressures obtaining on either side of the fixed orifice 50, and at the other end acted upon by a spring 56. The supply of pressure fluid to operate the piston 53 is derived from the pump 3 through a pressure line 57, and movements of the shuttle valve 54 control the flow of pressure fluid to one side of the piston 53, the other side being connected to the relief conduit 47. Thus any alteration in the pressure differential developed across the fixed orifice 56, caused by any variation in the return flow from the fuel injection pumps, causes the shuttle valve 54 to move, and by means of the servo piston 53 to alter the effective area of the orifice 51, in such a manner as to restore the pressure differential to normal, and so to restore the volumetric rate of return flow to the predetermined constant value. The unit therefore maintains at all times a constant volumetric return flow from the pump chambers 1 and 2.

The metering orifice assembly 43 contains a sleeve valve 60 which is urged by a spring 61 into engagement with a cam 62 mounted on a shaft 63 under the control of a power lever 8 The sleeve valve 60 is formed with circumferentially spaced ports 64 through which the fuel is delivered to the conduit 44 and thence to the injection pump supply chambers 1 and 2. The lower end of the sleeve valve 60 cooperates with a conical valve member 65 to form a variable area metering orifice through which fuel is passed from a gallery 66 connected to the delivery side of the pump 3. The conical valve member 65 is mounted on a carrier member 67 which is held by a spring into engagement with an adjustable cam 68.

The pressures occurring on either side of the metering orifice are arranged to act on a flexible diaphragm 70 connected to a servo-control shuttle valve 17*, which is arranged to control the position of an injection pump setting piston 16 the servo pressure fluid for operating the piston 16*- being derived from the high pressure side of the metering orifice through a conduit 18. The assembly also includes limiting mechanism comprising an adjustable abutment 32 under the control of a cam 34 which may be set for normal running or for full power in positions determined by the stops 71 and 72.

The shaft 63 connected to the power lever 8 is connected to a slotted cam 75, which cooperates with a pin 76 engaging the slot to control the movements of a lever 77. One end of the lever 77 acts through a link 78 on the mid-point of a floating lever 79, and one end of this floating lever is connected through a shaft 80 and associated linkage with the control arms 13, 14, of the fuel injection pump assemblies. The other end of the floating lever 79 is connected through a bell crank lever 81 and linkage 82, 83, 84 to the injection pump setting piston 16.

The pin 76 engaging the slot in the cam 75 is mounted on a sliding element 85 within a fixed sleeve 86, and the lower end of the lever 77 is pivotally attached to an adjustable fulcrum 87, sliding in parallel guides 88 under the control of a lever 89. The fulcrum 87 is normally stationary.

The arrangement of the system is such that movements of the power lever 8 act through the floating lever 79 to adjust the setting of the injectionpumps to approximately the correct position, while at the same time the cam 62 on the shaft 63 sets the area of the metering orifice so as to provide the correct flow to the pumps, including the excess constant flow return passing through the flow control unit 46. Any slight inaccuracies in the setting of the injection pumps, or any variation in the delivery from the pumps to the engine, will result in a variation from the designed pressure difference developed across the metering orifice, 60, 65, and this pressure difference will act through the diaphragm 70, and the valve 17 and piston 16, and the linkage including the floating lever 79, to adjust the setting of the fuel injection pumps. It will be seen that since the setting of the fuel injection pumps is directly mechanically connected to the power lever 8", the response of the pumps to movements of the power lever is instantaneous, and the injection pumps are not controlled wholly by the pressure difference developed across the metering orifice, through fine adjustments of the pump setting are carried out in accordance with this pres.- sure ditference.

The cam 68 provides means for effecting additional adjustment of the metering orifice, for example to give a reduction in the fuel delivered to the engine under certain operating conditions. Thus if the engine is used as an aircraft power unit it may be necessary to reduce the quantity of fuel supplied to the engine above the critical altitude, that is to say the altitude above which the engine supercharger is incapable of maintaining the required supercharging pressure. In this case the apparatus for adjusting the setting of the cam 58 is conveniently linked also to the rod 89 adjusting the fulcrum of the lever 77, so that the mechanism also effects a direct reduction of the setting of the injection pumps.

In the example illustrated in Figure 2 the two fuel injection pump chambers 1 and 2 are supplied with fuel from a pump 3; via a metering assembly 91, and the excess of fuel is returned to the fuel tank 40 via a flow control unit 92. In this system however the metering unit 91 is arranged to provide a substantially constant flow of fuel to the injection pump supply chambers 1 and 2 for any setting of the power lever, while the return flow control unit 92 is arranged to adjust the setting of the fuel injection pumps in response to changes in the return flow from the pumps.

The metering unit 91 contains a sleeve valve 60 under the control of the power lever 8 acting through a shaft 63 and cam 62*. As in the system illustrated in Figure 1 a metering orifice is formed by a conical valve member 65 cooperating with the sleeve 60 this valve member being under the control of a cam 68. The differential pressure across the metering orifice is led to a flexible diaphragm 70* connected as before to a servo control shuttle valve 17 but in this case the shuttle valve controls the position of a piston 93 connected to a conical valve member 94 lying in an orifice 95 in a by-pass conduit 96 between the output and input sides of the pump 36. The shuttle valve 17* and the piston 93 act to :control the effective area of the orifice 95 and so to control the effective volumetric delivery from the pump to the main metering orifice formed by the parts 60 and 65*, at a constant value as determined by the setting of this main orifice. For any setting of the power lever 8' therefore a predetermined constant flow of fuel to the injection pumps supply chambers 1 and 2 is maintained.

The return flow control unit 92 includes a fixed metering orifice 50 through which the whole of the return flow of fuel passes from the chambers 1 and 2, and in series with this orifice a pressure relief valve 100 which maintains a predetermined back pressure in the supply chambers 1 and 2. After passing through the valve 100 the excess fuel is returned to the tank 40 via a return conduit 47.

The pressure difference across the fixed orifice 50 is arranged to act on a flexible diaphragm 55 through a balanced servo control shuttle valve 54 which controls the position of the servo piston 53 The piston 53 is mechanically connected through a linkage 101, 102 to one end of a floating lever 103, the other end of which is connected through a shaft 104 to the arms 13 and 14 controlling the setting of the fuel injection pumps. The mid-point of the floating lever 103 is connected to a member 105 sliding in parallel guides 106, and the other end of the member 105 is connected to a pin 107 engaging a slot in a cam 108 mounted on a shaft 63 Any variation in the return flow from the pump supply chambers 1 and 2 will cause a corresponding variation in the pressure difference created across the fixed orifice 50 and this pressure difference will act through the diaphragm 55 and servo control valve 54* to readjust the setting of the fuel injection pumps so as to maintain the return flow at the predetermined figure.

It will be seen that the power lever 8 is directly mechanically connected to the arms 13 and 14 controlling thesetting .of the fuel injection pumps, and movements of the power lever therefore provide instantaneous adjustment of the setting of the injection pumps. The power lever also controls directly through the cam 62 the setting of the main metering orifice in the unit 91, and any variation in the fuel delivered to the engine by the injection pumps is maintained constant by the unit 92, as

described above.

What I claim as my invention and desire to secure by Letters Patent is: i I

1. Fuel injection apparatus for a reciprocating internal combustion engine of the liquid fuel injection type comprlslng a reciprocating positive displacement fuel injection pump, a pump supply chamber from which the pump delivers fuel to the engine, mechanism for varying the rate at which fuel is delivered by the pump to the engine, means for supplying fuel to and for continuously removing excess fuel from the pump supply chamber at a controlled net rate of flow, including a metering orifice in both the inlet and outlet connections to the pump supply chamber arranged so that the volumetric rate of fuel flow there through determines the net volumetric rate at which fuel is supplied from the injection pump supply chamber to the engine, means for maintaining a controlled rate of flow through one of 'said orifices and pressure responsive means arranged to be responsive to changes in the pressure developed across the second orifice, and to act on the control mechanism for varying the quantity of fuel dellivered by the pump to the engine, in a sense tending to maintain the pressure developed across the said second orifice at a constant value, and hence to maintain a constant controlled delivery of fuel from the pump to the engine.

2. Fuel injection apparatus as claimed in claim 1 including master control means linked with and arranged to adjust the effective cross sectional area of one of the orifices, in relation to the pressure difference developed across said orifice, so as to vary the net volumetric supply of fuel to the pump supply chamber, the said master control means being linked also with the said pump control mechanism to vary the rate at which fuel is delivered by the pump to the engine.

3. Fuel injection apparatus as claimed in claim 1 in which the second metering orifice, which is associated with the said pressure responsive means is arranged in the inlet connection to the injection pump supply chamber, and including master control means linked with and arranged to adjust the effective cross sectional area of this orifice in relation to the pressure difference developed across the orifice, so as to vary the net volumetric supply of fuel to the pump supply chamber, while the first metering orifice is arranged in the outlet connection from the pump supply chamber, and is of fixed cross sectional area, and means are provided for Varying the flow through the outlet connection in accordance with the pressure difference developed across this first orifice, so as to maintain a constant fuel flow through the outlet connection from the pump supply chamber.

4. Fuel injection apparatus as claimed in claim 3 in which the master control means is linked with the said pump control mechanism to vary the rate at which fuel is delivered by the pump to the engine.

5. Fuel injection apparatus as claimed in claim 1 in which the second metering orifice the pressure drop across which is arranged to control the control mechanism for varying the fuel delivered to the engine by the pump, is

of fixed cross sectional area and is arranged in the outlet connection from the pump supply chamber, while the first metering orifice is arranged in the inlet to the pump supply chamber, and including master control means arranged to adjust the cross sectional area in relation to the pressure difference developed across this orifice, so as to vary the net volumetric supply of fuel to the pump supply chamber.

6. Fuel injection apparatus as claimed in claim 5 in which the master control means is linked with the said pump control mechanism to vary the rate at which fuel is delivered by the pump to the engine.

7. Fuel injection apparatus as claimed in claim 1 including means for providing an adjustable limit to the movement of the control mechanism for varying the rate at which fuel is delivered by the pump to the engine.

8. Fuel injection apparatus as claimed in claim 1 including means for varying automatica llytthe effective cross sectional area of one of the orifices in accordance with the specific gravity of the fuel, so as to control the mass fuel flow delivered by the pump to the engine.

References Cited in the file of this patent UNITED STATES PATENTS 

